WO2019121673A1 - Suppression de paquets pdcp pour réduire la charge de réseau dans des scénarios de connectivité multiple - Google Patents

Suppression de paquets pdcp pour réduire la charge de réseau dans des scénarios de connectivité multiple Download PDF

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Publication number
WO2019121673A1
WO2019121673A1 PCT/EP2018/085482 EP2018085482W WO2019121673A1 WO 2019121673 A1 WO2019121673 A1 WO 2019121673A1 EP 2018085482 W EP2018085482 W EP 2018085482W WO 2019121673 A1 WO2019121673 A1 WO 2019121673A1
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packet
node
pdcp
nodes
layer
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PCT/EP2018/085482
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English (en)
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Nurul MAHMOOD
Daniela Laselva
Klaus Ingemann Pedersen
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Nokia Technologies Oy
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
    • H04L69/30—Definitions, standards or architectural aspects of layered protocol stacks
    • H04L69/32—Architecture of open systems interconnection [OSI] 7-layer type protocol stacks, e.g. the interfaces between the data link level and the physical level
    • H04L69/321—Interlayer communication protocols or service data unit [SDU] definitions; Interfaces between layers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W40/00—Communication routing or communication path finding
    • H04W40/02—Communication route or path selection, e.g. power-based or shortest path routing
    • H04W40/12—Communication route or path selection, e.g. power-based or shortest path routing based on transmission quality or channel quality
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1829—Arrangements specially adapted for the receiver end
    • H04L1/1835—Buffer management
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1867—Arrangements specially adapted for the transmitter end
    • H04L1/189—Transmission or retransmission of more than one copy of a message
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1867—Arrangements specially adapted for the transmitter end
    • H04L1/1896—ARQ related signaling
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L47/00—Traffic control in data switching networks
    • H04L47/10—Flow control; Congestion control
    • H04L47/32—Flow control; Congestion control by discarding or delaying data units, e.g. packets or frames
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L69/00—Network arrangements, protocols or services independent of the application payload and not provided for in the other groups of this subclass
    • H04L69/22—Parsing or analysis of headers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/15—Setup of multiple wireless link connections
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02—Terminal devices

Definitions

  • This invention relates generally to multi-connectivity (such as dual connectivity) in wireless communication networks and, more specifically, relates to packet data convergence protocol packet routing in these networks.
  • Dual connectivity as standardized by 3GPP in LTE Releases 12/13, extends the LTE-Advanced carrier aggregation (CA) functionality to allow a user equipment (UE) to simultaneously receive/send data from two different eNBs. So far DC has been proposed as a solution to boost throughput performance, using data split at a PDCP layer.
  • CA LTE-Advanced carrier aggregation
  • a method comprises receiving a packet at a first node in a communications network and duplicating, by the first node, the packet to form copies of the packet.
  • the method includes flagging, by the first node, each of two data units, each comprising one of the copies, with information indicating the
  • the method also includes sending, by the first node, one of the data units, with one of the copies, through a plurality of protocol layers toward transmission via an air interface toward a user equipment.
  • the method further includes sending, by the first node, another of the data units, with the other copy, over a network interface and toward one or more nodes.
  • An additional exemplary embodiment includes a computer program, comprising code for performing the method of the previous paragraph, when the computer program is run on a processor.
  • An exemplary apparatus includes one or more processors and one or more memories including computer program code.
  • the one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to perform at least the following: receiving a packet at a first node in a communications network; duplicating, by the first node, the packet to form copies of the packet; flagging, by the first node, each of two data units, each comprising one of the copies, with information indicating the corresponding data unit comprises a copy of the packet; sending, by the first node, one of the data units, with one of the copies, through a plurality of protocol layers toward transmission via an air interface toward a user equipment; and sending, by the first node, another of the data units, with the other copy, over a network interface and toward one or more nodes.
  • An exemplary computer program product includes a computer-readable storage medium bearing computer program code embodied therein for use with a computer.
  • the computer program code includes: code for receiving a packet at a first node in a communications network; code for duplicating, by the first node, the packet to form copies of the packet; code for flagging, by the first node, each of two data units, each comprising one of the copies, with information indicating the corresponding data unit comprises a copy of the packet; code for sending, by the first node, one of the data units, with one of the copies, through a plurality of protocol layers toward transmission via an air interface toward a user equipment; and code for sending, by the first node, another of the data units, with the other copy, over a network interface and toward one or more nodes.
  • an apparatus comprises: means for receiving a packet at a first node in a communications network; means for duplicating, by the first node, the packet to form copies of the packet; means for flagging, by the first node, each of two data units, each comprising one of the copies, with information indicating the corresponding data unit comprises a copy of the packet; means for sending, by the first node, one of the data units, with one of the copies, through a plurality of protocol layers toward transmission via an air interface toward a user equipment; and means for sending, by the first node, another of the data units, with the other copy, over a network interface and toward one or more nodes.
  • a method in an exemplary embodiment, includes receiving a data unit at a node of a set of nodes in a communications network, wherein the node receives in the data unit a copy of a packet that is also sent via one or more other nodes in the set of nodes toward a user equipment.
  • the data unit comprises information indicating the corresponding data unit comprises a copy of the packet.
  • the method includes forwarding the data unit with the packet to a first protocol layer of a plurality of layers toward transmission via an air interface toward the user equipment.
  • the method includes discarding, in the first protocol layer or in a layer lower than the first protocol layer, the packet in response to receiving an acknowledgement at the node that a copy of the packet was successfully received by the user equipment.
  • An additional exemplary embodiment includes a computer program, comprising code for performing the method of the previous paragraph, when the computer program is run on a processor.
  • An exemplary apparatus includes one or more processors and one or more memories including computer program code.
  • the one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to perform at least the following: receiving a data unit at a node of a set of nodes in a communications network, wherein the node receives in the data unit a copy of a packet that is also sent via one or more other nodes in the set of nodes toward a user equipment, the data unit comprising information indicating the corresponding data unit comprises a copy of the packet; forwarding the data unit with the packet to a first protocol layer of a plurality of layers toward transmission via an air interface toward the user equipment; and discarding, in the first protocol layer or in a layer lower than the first protocol layer, the packet in response to receiving an acknowledgement at the node that a copy of the packet was successfully received by the user equipment.
  • An exemplary computer program product includes a computer-readable storage medium bearing computer program code embodied therein for use with a computer.
  • the computer program code includes: code for receiving a data unit at a node of a set of nodes in a communications network, wherein the node receives in the data unit a copy of a packet that is also sent via one or more other nodes in the set of nodes toward a user equipment, the data unit comprising information indicating the corresponding data unit comprises a copy of the packet; code for forwarding the data unit with the packet to a first protocol layer of a plurality of layers toward transmission via an air interface toward the user equipment; and code for discarding, in the first protocol layer or in a layer lower than the first protocol layer, the packet in response to receiving an acknowledgement at the node that a copy of the packet was successfully received by the user equipment.
  • an apparatus comprises: means for receiving a data unit at a node of a set of nodes in a communications network, wherein the node receives in the data unit a copy of a packet that is also sent via one or more other nodes in the set of nodes toward a user equipment, the data unit comprising information indicating the corresponding data unit comprises a copy of the packet; means for forwarding the data unit with the packet to a first protocol layer of a plurality of layers toward transmission via an air interface toward the user equipment; and means for discarding, in the first protocol layer or in a layer lower than the first protocol layer, the packet in response to receiving an acknowledgement at the node that a copy of the packet was successfully received by the user equipment.
  • FIG. 1 is a block diagram of one possible and non-limiting exemplary system in which the exemplary embodiments may be practiced;
  • FIG. 2 illustrates NR DC/MC operation with data duplication in the downlink direction
  • FIG. 3 shows exemplary packet transfer through different protocol layers in an apparatus such as a gNB or UE;
  • FIG. 4 illustrates an example of a PDCP header, and this figure is a modified copy of Figure 6.2.2.3-1,“PDCP Data PDU format for DRBs with 18 bits PDCP SN
  • FIG. 5 illustrates NR DC/MC operation with data duplication in the downlink direction, in accordance with an exemplary embodiment
  • FIG. 6 is a message flow diagram of a process for flushing PDCP packets to reduce network load in multi-connectivity scenarios, and is performed by a duplicating node;
  • FIG. 7 is a logic flow diagram of part of a process for flushing PDCP packets to reduce network load in multi-connectivity scenarios, and is performed by an anchor node.
  • the exemplary embodiments herein describe techniques for flushing PDCP packets to reduce network load in multi-connectivity scenarios. Additional description of these techniques is presented after a system into which the exemplary embodiments may be used is described.
  • FIG. 1 shows a block diagram of one possible and non limiting exemplary system in which the exemplary embodiments may be practiced.
  • FIG. 1 shows a block diagram of one possible and non limiting exemplary system in which the exemplary embodiments may be practiced.
  • a user equipment (UE) 110 is in wireless communication with a wireless communications network 100.
  • a UE is a wireless, typically mobile device that can access a wireless communications network 100.
  • the UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected through one or more buses 127.
  • Each of the one or more transceivers 130 includes a receiver, Rx, 132 and a transmitter, Tx, 133.
  • the one or more buses 127 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, and the like.
  • the one or more transceivers 130 are connected to one or more antennas 128.
  • the one or more memories 125 include computer program code 123. For instance, the one or more memories 125 and the computer program code 123 may be configured to, with the one or more processors 120, cause the user equipment 110 to perform one or more of the operations
  • the UE 110 communicates with gNB 170-1 via a wireless link 111-1 and communicates with gNB 170-2 with wireless link 111-2.
  • gNB 170-1 there are two gNBs 170, although there could be three or more (as indicated by ellipses 187).
  • the gNB 170-1 is referred to as an anchor node, and the gNB 170-2 is referred to a duplicating node, and these terms are described in more detail below.
  • One exemplary possible internal configuration for the gNB 170-1 is described below, and it is assumed that the internal configuration for the gNB 170-2 is similar, and therefore only potential differences are described below.
  • Each gNB (evolved NodeB) 170 is a base station (e.g., for NR) that provides access by wireless devices such as the UE 110 to the wireless communications network 100.
  • the gNB 170-1 includes one or more processors 152, one or more memories 155, one or more network interfaces (N/W I/F(s)) 161, and one or more transceivers 160 interconnected through one or more buses 157.
  • Each of the one or more transceivers 160 includes a receiver, Rx, 162 and a transmitter, Tx, 163.
  • the one or more transceivers 160 are connected to one or more antennas 158.
  • the one or more memories 155 include computer program code 153.
  • the gNB 170-1 includes a protocol stack 150, comprising one of or both parts 150-1 and/or 150-2, which may be implemented in a number of ways.
  • the protocol stack 150 may be implemented in hardware as protocol stack 150-1, such as being implemented as part of the one or more processors 152.
  • the protocol stack 150-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array.
  • the protocol stack 150 may be implemented as protocol stack 150-2, which is implemented as computer program code 153 and is executed by the one or more processors 152.
  • the one or more memories 155 and the computer program code 153 are configured to, with the one or more processors 152, cause the gNB 170-1 to perform one or more of the operations as described herein.
  • the one or more network interfaces 161 communicate over a network such as via the links 176 and 131.
  • Two or more gNBs 170 communicate using, e.g., link 176.
  • the link 176 may be wired or wireless or both and may implement, e.g., an Xn interface for a gNB.
  • the one or more buses 157 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, wireless channels, and the like.
  • the one or more transceivers 160 may be implemented as a remote radio head (RRH) 195, with the other elements of the gNB 170-1 being physically in a different location from the RRH, and the one or more buses 157 could be implemented in part as fiber optic cable to connect the other elements of the gNB 170-1 to the RRH 195.
  • RRH remote radio head
  • the gNB 170-2 includes a protocol stack 151 that may be implemented in hardware as protocol stack 151-1, such as being implemented as part of the one or more processors 152.
  • the protocol stack 151-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array.
  • the protocol stack 151 may be implemented as protocol stack 151-2, which is implemented as computer program code 153 and is executed by the one or more processors 152.
  • the one or more memories 155 and the computer program code 153 are configured to, with the one or more processors 152, cause the gNB 170-2 to perform one or more of the operations as described herein.
  • the wireless network 100 may include a network control element (NCE) 190 that may include MME (Mobility Management Entity)/SGW (Serving Gateway)
  • NCE network control element
  • MME Mobility Management Entity
  • SGW Serving Gateway
  • the gNB 170 is coupled via a link 131 to the NCE 190.
  • the link 131 may be implemented as, e.g., an Sl interface.
  • the NCE 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N/W I/F(s)) 181, interconnected through one or more buses 185.
  • the one or more memories 171 include computer program code 173.
  • the one or more memories 171 and the computer program code 173 are configured to, with the one or more processors 175, cause the NCE 190 to perform one or more operations.
  • the wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network.
  • Network virtualization involves platform virtualization, often combined with resource virtualization.
  • Network virtualization is categorized as either external, combining many networks, or parts of networks, into a virtual unit, or internal, providing network-like functionality to software containers on a single system. Note that the virtualized entities that result from the network virtualization are still implemented, at some level, using hardware such as processors 152 or 175 and memories 155 and 171, and also such virtualized entities create technical effects.
  • the computer readable memories 125, 155, and 171 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.
  • the computer readable memories 125, 155, and 171 may be means for performing storage functions.
  • the processors 120, 152, and 175 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples.
  • the processors 120, 152, and 175 may be means for performing functions, such as controlling the UE 110, gNB 170, and other functions as described herein.
  • NR DC/MC operation with data duplication in the downlink (DL) direction is schematically presented in FIG. 2.
  • the gNB 170-1 which is in control of the PDCP duplication, is called the PDCP anchor node (or the MgNB), whereas any other gNB 170-2 serving the duplicated PDCP packet for a given UE is termed as the PDCP duplicating node (or the SgNB).
  • the following layers are shown in each of the gNBs: PDCP layer 302, RLC layer 303, MAC layer 304, and PHY layer 305.
  • the packet 210 may be duplicated at the PDCP layer 302 and, if so, the duplicated packet 210-1 is forwarded to the PDCP duplicating gNB node(s) 170-2 (of which only one is shown in FIG. 2) over the Xn interface via link 235.
  • the same data packet i.e., PDCP PDU 312, with a given sequence number, SN
  • PDCP PDU 312 with a given sequence number, SN
  • one PDCP PDU 312 travels via path 230 through the layers of the anchor node gNB 170-1 and then through the air interface and link 111-1 to the UE 110, and the packet 210 travels via PDCP PDU 312 through the link 235 then through path 245 (and layers 302-305) of the duplicating node 170-2 and the air interface and link 111-2 to the UE 110.
  • the set 180 of gNBs 170 i.e., 170-1 and one or more of 170-2) transmitting the duplicated packet is termed in this document as the duplication set.
  • FIG. 3 shows the packet transfer through the different protocol layers for apparatus such as a gNB.
  • Multiple layers are illustrated: SDAP layer 301, PDCP layer 302, RLC layer 303, and MAC layer 304. These are listed in order from an upper layer (SDAP layer 301) to a lower layer PCDP layer 302, to an even lower layer (RLC layer 303), to an even lower layer (MAC layer 304).
  • SDAP layer 301 an upper layer
  • PCDP layer 302 an even lower layer
  • MAC layer 304 even lower layer
  • the lowest layer is the PHY layer 305, shown in FIGS. 2 and 5), and the highest layer shown is the SDAP layer 301. Note that“lower” and“upper” layers are defined as such for this well-known protocol stack.
  • an IP packet 3l0-n is formed into an SDAP SDU 31 l-n with header (H) in the SDAP layer 301, which itself is formed into a PDCP SDU 312-h plus header (H) in the PDCP layer 302, which is then formed into an RLC SDU 313-h plus header (H) in the RLC layer 303, which then is packaged into the MAC PDU transport block (TB) 320-1 via the MAC SDU 3l4-n and its header (H).
  • the IP packet 3l0-n+l is similarly formed into an SDAP SDU 31 l-n+l with header (H) in the SDAP layer 301, which itself is formed into a PDCP SDU 3l2-n+l plus header (H) in the PDCP layer 302, which is then formed into an RLC SDU 3l3-n+l plus header (H) in the RLC layer 303, which then is packaged into the MAC PDU transport block (TB) 320-1 via the MAC SDU 3l4-n+l and its header (H).
  • the IP packet 3l0-m is similarly handled into the SDAP SDU 31 l-m and the PDCP SDU 3 l2-m.
  • the“front” part of the header H and PDCP SDU 3l2-m is put into an SDU segment 313 -ml and header (H) in the RLC layer 303 and then used to fill the rest of the MAC PDU transport block 320-1 via the MAC SDU 3l4-ml and its header (H).
  • The“back” part of the PDCP SDU 3 l2-m is put into an SDU segment 3 l3-m2 and header (H) in the RLC layer 303 and then used to fill the beginning of the (next) MAC PDU transport block 320-2 via the MAC SDU 3l4-m2 and its header (H).
  • the SDUs are packaged into PDUs, which include the headers (Hs).
  • Hs headers
  • the combination of the header (H) and the SDAP SDU make an SDAP PDU. This is the same for the other layers 302, 303, and 304.
  • a HARQ mechanism is part of the MAC layer 304, operated independently for each link (e.g., node).
  • HARQ positive acknowledgment (ACK) signaling for each physical layer (PHY) transmission is sent to the transmitting gNB. That is, the transmission from the anchor gNB 170-1 is acknowledged by the UE 110 to the anchor gNB 170-1, and that ACK will provide the indication that the PDCP PDUs mapped to the transmission were successfully received.
  • UM RLC unacknowledged mode
  • no RLC ACKs e.g., RLC status reports
  • the MAC-layer transmission from the duplicating gNB 170-2 is acknowledged from the UE 110 to that particular gNB 170-2. It should be noted that the duplicating gNB will provide the indication of successful delivery to the anchor gNB 170-1 by means of flow control (i.e., PDCP-level data status delivery procedure over Xn).
  • flow control i.e., PDCP-level data status delivery procedure over Xn.
  • a duplicated PDCP packet is successfully received at the UE, two different situations concerning this particular duplicated packet can be identified in the duplicating nodes, namely that particular PDCP packet is either in the PDCP buffer awaiting transmission, or it is in the lower layer undergoing MAC-level HARQ transmission/retransmission.
  • Examples include introduction of a PDCP time-out timer whereby a PDCP packet is‘flushed’ from the PDCP buffer after a predefined time; and sending a PDCP duplication status report to all the gNBs in the duplication set to indicate the receipt of a duplicated PDCP packet at the UE (see below for details).
  • most of the proposed solutions are aimed at discarding the PDCP packet when the packet is still at the PDCP buffer awaiting transmission from the duplicating nodes.
  • packets duplicated to boost reliability will most likely be prioritized for transmission from the PDCP buffer.
  • many of the duplicated packets that have not reached the UE 110 may in fact be undergoing transmission/retransmission at the lower layers, i.e. at the RLC and MAC layers (including potential HARQ retransmissions).
  • DC flow control mechanisms are specified for the (secondary node) SN to provide indication to the master node (MN) of the status of the data forwarded from the MN (see X2 interface specification, e.g., in 3GPP TS 36.423).
  • LWA status report includes the following fields:
  • FMS First missing sequence number
  • HRW Highest received SN on WLAN
  • NMP Number of missing PDUs
  • Proposal 1 In case of PDCP duplication in EN-DC, it is proposed to remove the buffered PDCP PDUs in one node if they have already been successfully delivered to the UE in another node.
  • Proposal 2 Based on the DDDS (Dynamic Delegation Discovery System) report from the splitting node, the anchor node should be able to remove the buffered PDCP PDUs which have already been transmitted to the UE via the splitting node.
  • DDDS Dynamic Delegation Discovery System
  • Proposal 3 Based on the DDDS report from the anchor node with indication of delivered PDU SN, the splitting node can remove the corresponding PDCP PDU in the buffer.
  • This disclosure introduces an exemplary method in an example to keep track at a gNB of the lower layer packets (e.g., RLC/MAC PDUs) mapped to duplicated PDCP PDUs, to quickly identify and discard those pending RLC/MAC packets, which are associated to PDCP PDUs already successfully received by the UE 110 through any of the legs in the duplication set, this way reducing and/or preventing their unnecessary
  • the exemplary steps can be specifically identified, namely: [0058] 1) PDCP packets selected for duplication are flagged at the PDCP anchor node 170-1 to identify them as duplicated packets;
  • step 2 For packets flagged according to step 1, a bookkeeping mechanism is introduced at all of the duplicating nodes 170-2, to keep track of the identifiers of the lower layer packets (e.g., RLC/MAC PDUs) which carry the duplicated PDCP packets; and
  • the lower layer packets e.g., RLC/MAC PDUs
  • the gNB can discard the PDCP PDU also if the packet has already left the PDCP layer and is pending in the lower layers (e.g., in the MAC pending HARQ retransmission) based on the mapping mechanism introduced in step 2.
  • the duplicating gNB 170-2 can determine that the packet has been sent to the lower layers and is buffered at the lower layers.
  • PDCP PDU packets selected for duplication are flagged at the PDCP-anchor node 170-1 to identify the packets were duplicated, so their lower layer identifiers can be tracked both at the PDCP-anchor node and duplicating nodes.
  • the PDCP-anchor gNB 170-1 In order for the PDCP-anchor gNB 170-1 to flag duplicated PDCP PDU packets, this could be achieved in-band (i.e., to be carried as part of the packet itself), e.g., either using one of the existing control information bits in the packet header or adding or appending one additional bit (e.g., or more bits) in the header to indicate the duplication flag.
  • the duplication flag (e.g., one bit, where“1” might mean this packet is duplicated) can be inserted as part of the PDCP header using one of the reserved (R) bits.
  • FIG. 4 illustrates an example of a PDCP header 400 with a number of reserved bits 410. This figure is a modified copy of Figure 6.2.2.3-1,“PDCP Data PDU format for DRBs with 18 bits PDCP SN (applicable for UM DRBs and AM DRBs)”, from 3GPP TS 38.323 VI.0.1 (2017-10).
  • the anchor gNB 170-1 could insert a duplication flag using one of the reserved bits in, e.g., RFC/MAC headers - assuming one-to- one mapping between a PDCP PDU and RFC/MAC PDU, e.g., thanks to the limited payload size expected for URFFC traffic. While only the PDCP packets are sent over the Xn interface, when the duplicating node 170-2 receives a PDCP packet (with duplication flag set), the node can set a similar flag when sending the packet to RFC/MAC layers 303/304.
  • FIG. 5 illustrates NR DC/MC operation with data duplication in the downlink direction, in accordance with an exemplary embodiment.
  • the protocol stack 150 in the PDCP anchor node 170-1 is shown comprising the following layers: PDCP layer 302, RLC layer 303, MAC layer 304, and PHY layer 305.
  • the protocol stack 151 in the PDCP duplicating node 170-2 is shown comprising the following layers: PDCP layer 302, RLC layer 303, MAC layer 304, and PHY layer 305. Relative to FIG. 2, some or all of the layers 302-305 could be modified to implement the exemplary embodiments for the protocol stacks 150 and 151.
  • Step (1) is shown via the block 510, which indicates that duplicated packets are flagged and forwarded, by the anchor node 170-1, to the duplicating node 170-2.
  • the anchor node 170-1 adds a duplication flag 540 into the PDCP PDU 312 (in this example) and in this example to create a packet 210’ which then is packaged into the PDCP PDU 312.
  • the modified PDCP PDU 312’ is sent via the link 235 to the duplication node 170-2, which might remove the duplication flag 540 from the modified PDCP PDU 312 sometime after reception of the PDCP PDU 312, depending on
  • the duplication flag 540 is left in the PDCP PDU 312 to alert the lower layers 303/304 that bookkeeping should be performed, although other techniques to indicate this could be used.
  • the modified PDCP PDU 312’ is also sent via the link 230 toward the PHY layer 305 for transmission over the link 111-1 toward the UE 110.
  • blocks 510 and 520 indicate the operation of an exemplary method, a result of execution of computer program instructions embodied on a computer readable memory, functions performed by logic implemented in hardware, and/or interconnected means for performing functions in accordance with exemplary embodiments.
  • a bookkeeping mechanism may be used to keep track of the lower layer identifiers of the duplicated PDCP packets.
  • the buffering options and the traffic load it can take some time before a PDCP packet that has left the PDCP buffer is actually transmitted and successfully received by the UE. For instance, the packet may be queued, e.g., at the RLC/MAC buffer of the duplicating node 170-2 awaiting scheduling decisions, or the packet may undergo a physical- level
  • retransmission (e.g., HARQ retransmission).
  • an exemplary embodiment proposes that the lower layers maintain a bookkeeping (e.g., a mapping table) of the duplicated PDCP packets by keeping track of the mapping between PDCP ID (e.g., a PDCP PDU SN) and lower layer packet identifiers, as depicted in reference number 520 of FIG. 5. These are also described in FIGS. 6 and 7.
  • a bookkeeping e.g., a mapping table
  • the node 170-2 when a node 170-2 receives an ACK related to PDCP packets undergoing transmission, the node 170-2 can forward a discard message to the lower layers with the relevant PDCP ID (e.g., PDCP PDU SN).
  • the lower layers can then identify the successfully received packet(s) using the proposed mapping between PDCP ID and lower layer IDs, and discard the packet.
  • the duplicated PDCP packet discard message flow is depicted in FIG. 6.
  • this process of discarding packets in response to an ACK being received may also occur on the PDCP anchor node 170-1. That is, the UE 110 may send an ACK to the PDCP anchor node 170-1 that the UE 110 has received a packet from the PDCP duplicating node 170-2, and the PDCP anchor node 170-1 would then discard the packet if the packet has not yet been sent or has been sent and is buffered, as described in more detail below.
  • the ACK for a packet received by the UE from the PDCP duplicating node 170-2 may, depending on implementation, get sent by the UE 110 to the PDCP anchor node 170-1 or by the UE 110 to the PDCP duplicating node 170-2 and from the PDCP duplicating node 170-2 to the PDCP anchor node 170-1.
  • FIG. 6 is a flow diagram of a process 600 for flushing PDCP packets to reduce network load in multi-connectivity scenarios.
  • FIG. 6 illustrates the operation of an exemplary method or methods, a result of execution of computer program instructions embodied on a computer readable memory, functions performed by logic implemented in hardware, and/or interconnected means for performing functions in accordance with exemplary embodiments.
  • the duplicating gNB 170-2 causes the blocks 600 in FIG. 6 to be performed, e.g., under control in part of the protocol stack 151.
  • the PDCP duplicating node 170-2 receives a PDCP packet with a duplication flag 540 set.
  • the PDCP duplicating node 170-2 in block 605 starts mapping and communication processes for this packet. For instance, the PDCP duplicating node 170- 2, as part of the communication process, can send the packet through the path 245, to be transmitted by the PHY layer 305 at some point.
  • the PDCP duplicating node 170-2 can set up a mapping for this packet, e.g., using the PDCP ID, which mapping indicates this is a duplicated packet. This might be performed, in an exemplary embodiment, by use of a bookkeeping table 650, having one or more entries 655, in this example having entries 655-1 through 655-N. Each entry 655 might include one or more a PDCP ID, RLC ID, MAC ID, and/or PHY ID.
  • the PDCP duplicating node 170-2 also in block 640 has the lower layers map the PDCP ID to lower layer ID(s) (such as RLC ID(s), MAC ID(s) and/or PHY ID(s)) using bookkeeping. These IDs can be anything that might be used to uniquely identify a packet, such as a sequence number (SN).
  • the bookkeeping e.g., via the table 650 or some other data structure, allows a lower layer 303/304/305 to determine which packet should be discarded, e.g., in response to a message from upper layer(s).
  • block 640 can be considered to be a version of block 520 of FIG. 5.
  • the nodes 170 could include the PDCP anchor node 170-1 or another PDCP
  • duplicating node 170-2. If the ACK has been received by itself (block 612 Self), the flow for the PDCP duplicating node 170-2 proceeds to block 617, where the PDCP anchor node 170-1 sends an indication of the ACK to every node 170-1/2 (the PDCP anchor node 170-1 or another PDCP duplicating node 170-2) in the duplication set 180, and removes the packet from the mapping and ends.
  • the PDCP duplicating node 170-2 forwards a discard message to lower layers (e.g., the following layers: RLC layer 303, MAC layer 304, and PHY layer 305).
  • Blocks 635 and 645 are performed by the lower layer(s) 303, 304, and/or 305.
  • Block 635 indicates the lower layer(s) map the PDCP ID to corresponding lower layer ID(s) using bookkeeping, such as by using entries 655 in the bookkeeping table 650.
  • Block 645 indicates that one or more of the lower layers 303, 304, and/or 305 will discard (e.g., flush) the packet based on the forwarded discard message. This discarding uses the bookkeeping from block 635 in order to determine the correct packet to discard.
  • the PDCP duplicating node 170-2 might also remove this packet from the mapping (e.g., in an entry 655 in the bookkeeping table 650) and end the flow.
  • FIG. 7 is a logic flow diagram of part of a process for flushing PDCP packets to reduce network load in multi-connectivity scenarios.
  • FIG. 7 is performed by the anchor node 170-1.
  • This figure further illustrates the operation of an exemplary method or methods, a result of execution of computer program instructions embodied on a computer readable memory, functions performed by logic implemented in hardware, and/or interconnected means for performing functions in accordance with exemplary embodiments.
  • the protocol stack 150 may include multiples ones of the blocks in FIG. 7, where each included block is an interconnected means for performing the function in the block.
  • the blocks in FIG. 7 are assumed to be performed by the anchor node 170-1, e.g., under control of the protocol stack 150 at least in part.
  • the anchor node 170-1 determines to duplicate a received packet, e.g., an IP packet 310.
  • the anchor node 170-1 in block 720 flags the PDU (e.g., PDCP PDU 312) used to hold duplicated packet with a duplication flag 540 to create a modified PDU (e.g., modified PDCP PDU 312’).
  • the duplication flag 540 might be implemented in an exemplary embodiment by using a reserved bit (or bits) 410 in the PDCP Data PDU format of the PDCP header 400 (see block 721) or by appending a bit (or bits) to the header to expand the header by a bit (or bits) (see block 722).
  • the anchor node 170-1 in block 730 forwards the modified PDU (with the duplication flag) toward one or more duplicating nodes 170-2. This occurs via path 235.
  • blocks 720 and 730 may be considered to be a version of block 510 from FIG. 5.
  • the PDCP anchor node 170-1 starts mapping and communication processes for this packet in block 605.
  • Many of the subsequent operations in FIG. 7 are similar to or the same as those performed in FIG. 6.
  • a modified PDCP PDU 312’ is sent via path 230 in the PDCP anchor node 170-1 through the protocol layers 320/303/304/305 for
  • a received packet 210 is sent via two different pathways, one toward the UE (path 230) and one toward one or more duplicating nodes (path 235). It should be noted that the mapping and communication processes starting in block 610, and the operations performed in blocks 720 and 730 would typically be performed in parallel, such that the received packet is sent via the two different pathways in parallel.
  • the PDCP anchor node 170-1 can set up a mapping for this packet, e.g., using the PDCP ID, which mapping indicates this is a duplicated packet. As with FIG. 6, this might be performed, in an exemplary embodiment, by use of the bookkeeping table 650, having one or more entries 655, in this example having entries 655-1 through 655-N. Each entry 655 might include one or more a PDCP ID, RLC ID, MAC ID and/or PHY ID.
  • the PDCP anchor node 170-1 also in block 640 has the lower layers map the PDCP ID to lower layer ID(s) (such as RLC ID(s) and/or MAC ID(s)) using
  • the bookkeeping e.g., via the table 650 or some other data structure, allows a lower layer 303/304/305 to determine which packet should be discarded, e.g., in response to a message from upper layer(s).
  • the PDCP anchor node 170-1 determines if the ACK is from itself (e.g., from the UE 110 and via the protocol stack 150) or from duplicating node 170-2 in a duplication set 180.
  • the ACK for a packet received by the UE from the PDCP duplicating node 170-2 may, depending on implementation, get sent by the UE 110 to the PDCP anchor node 170-1 (and therefore up the protocol stack 150 to an appropriate layer) or by the UE 110 to the PDCP duplicating node 170-2 and from the PDCP duplicating node 170-2 to the PDCP anchor node 170-1.
  • the PDCP anchor node 170-1 sends an indication of the ACK to every duplicating node 170-2 in duplication set 180, and the packet is removed from the mapping (e.g., the entry 655 that corresponds to this packet in the bookkeeping table 650 is deleted or otherwise removed) and the flow ends.
  • the PDCP anchor node 170-1 forwards a discard message to lower layers (e.g., the following layers: RLC layer 303, MAC layer 304, and PHY layer 305).
  • Blocks 635 and 645 are performed by the lower layer(s) 303, 304, and/or 305.
  • Block 635 indicates the lower layer(s) map the PDCP ID to corresponding lower layer ID(s) using bookkeeping, such as by using entries 655 in the bookkeeping table 650.
  • Block 645 indicates that one or more of the lower layers 303, 304, and/or 305 will discard (e.g., flush) the packet based on the forwarded discard message. This discarding uses the bookkeeping from block 635 in order to determine the correct packet to discard.
  • the PDCP anchor node 170-1 might also remove this packet from the mapping (e.g., in an entry 655 in the bookkeeping table 650) and end the flow.
  • Embodiments herein may be implemented in software (executed by one or more processors), hardware (e.g., an application specific integrated circuit), or a combination of software and hardware.
  • the software e.g., application logic, an instruction set
  • a“computer-readable medium” may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer, with one example of a computer described and depicted, e.g., in FIG. 1.
  • a computer-readable medium may comprise a computer-readable storage medium (e.g., memories 125, 155, 171 or other device) that may be any media or means that can contain, store, and/or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.
  • a computer-readable storage medium does not comprise propagating signals.
  • the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined.
  • Tx transmitter UE user equipment e.g., a wireless, typically mobile device

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Abstract

Selon l'invention, un premier nœud reçoit un paquet, duplique le paquet pour former des copies, signale chacune de deux unités de données, comprenant chacune l'une des copies, avec des informations indiquant que l'unité de données correspondante comprend une copie. Le premier nœud envoie l'une des unités de données par l'intermédiaire de couches de protocole en vue d'une transmission à un équipement utilisateur (UE), et envoie l'autre des unités de données sur une interface réseau et vers un ou plusieurs nœuds. Un autre nœud reçoit dans une unité de données une copie du paquet. L'autre nœud transfère l'unité de données avec le paquet à une première couche de protocole parmi les multiples couches de protocole en vue d'une transmission par l'intermédiaire d'une interface radio vers l'UE. L'autre nœud supprime, dans la première couche de protocole ou dans une couche inférieure à la première, le paquet en réponse à la réception d'un accusé de réception (ACK) indiquant qu'une copie du paquet a été reçue avec succès par l'UE.
PCT/EP2018/085482 2017-12-22 2018-12-18 Suppression de paquets pdcp pour réduire la charge de réseau dans des scénarios de connectivité multiple WO2019121673A1 (fr)

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